System.IO.FileStream.FlushAsyncInternal C# (CSharp) Method

        private Task FlushAsyncInternal(CancellationToken cancellationToken)
        {
            if (cancellationToken.IsCancellationRequested)
                return Task.FromCanceled(cancellationToken);

            if (_fileHandle.IsClosed)
                throw Error.GetFileNotOpen();

            // The always synchronous data transfer between the OS and the internal buffer is intentional 
            // because this is needed to allow concurrent async IO requests. Concurrent data transfer
            // between the OS and the internal buffer will result in race conditions. Since FlushWrite and
            // FlushRead modify internal state of the stream and transfer data between the OS and the 
            // internal buffer, they cannot be truly async. We will, however, flush the OS file buffers
            // asynchronously because it doesn't modify any internal state of the stream and is potentially 
            // a long running process.
            try
            {
                FlushInternalBuffer();
            }
            catch (Exception e)
            {
                return Task.FromException(e);
            }

            if (CanWrite)
            {
                return Task.Factory.StartNew(
                    state => FlushOSBuffer(),
                    this,
                    cancellationToken,
                    TaskCreationOptions.DenyChildAttach,
                    TaskScheduler.Default);
            }
            else
            {
                return Task.CompletedTask;
            }
        }